cachefiles: Set object to close if ondemand_id < 0 in copen

If copen is maliciously called in the user mode, it may delete the request
corresponding to the random id. And the request may have not been read yet.

Note that when the object is set to reopen, the open request will be done
with the still reopen state in above case. As a result, the request
corresponding to this object is always skipped in select_req function, so
the read request is never completed and blocks other process.

Fix this issue by simply set object to close if its id < 0 in copen.

Signed-off-by: Zizhi Wo <wozizhi@huawei.com>
Signed-off-by: Baokun Li <libaokun1@huawei.com>
Link: https://lore.kernel.org/r/20240522114308.2402121-11-libaokun@huaweicloud.com
Acked-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Jia Zhu <zhujia.zj@bytedance.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/cachefiles/ondemand.c b/fs/cachefiles/ondemand.c
index 6f815e7c508674f6cc7a692ea323ad338b179308..922cab1a314b250f3dbddd4da9f721f56cec8314 100644 (file)
--- a/fs/cachefiles/ondemand.c
+++ b/fs/cachefiles/ondemand.c
@@ -182,6 +182,7 @@ int cachefiles_ondemand_copen(struct cachefiles_cache *cache, char *args)
        xas_store(&xas, NULL);
        xa_unlock(&cache->reqs);
 
+       info = req->object->ondemand;
        /* fail OPEN request if copen format is invalid */
        ret = kstrtol(psize, 0, &size);
        if (ret) {
@@ -201,7 +202,6 @@ int cachefiles_ondemand_copen(struct cachefiles_cache *cache, char *args)
                goto out;
        }
 
-       info = req->object->ondemand;
        spin_lock(&info->lock);
        /*
         * The anonymous fd was closed before copen ? Fail the request.
@@ -241,6 +241,11 @@ int cachefiles_ondemand_copen(struct cachefiles_cache *cache, char *args)
        wake_up_all(&cache->daemon_pollwq);
 
 out:
+       spin_lock(&info->lock);
+       /* Need to set object close to avoid reopen status continuing */
+       if (info->ondemand_id == CACHEFILES_ONDEMAND_ID_CLOSED)
+               cachefiles_ondemand_set_object_close(req->object);
+       spin_unlock(&info->lock);
        complete(&req->done);
        return ret;
 }